Automatic switching system



Nov, 11,

C. A. BUTCHER AUTOMATIC SWITCHING SYSTEM Filed Aug. 28 @922 2 Sheets-Sheet l INVENTOR Charles A. Butcher.

WITNESSES:

ATTORN EY C. A. BUTCHER AUTOMATIC SWITCHING SYSTEM Nov. 11, 1924- Filed Aug. 28, 2 Sheets-Sheet 2 de z .5 5 m WITNESSES:

Charles A. Butcher.

ATTORNEY Patented Nov. 11, 1924.

UNITED STATES- PATENT OFFICE.

CHARLES A. BUTCHER, OF EAST PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WEST- INGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OLE PENN- SYLVANIA.

' AUTOMATIC SWITCHING SYSTEM.

Application filed August 28, 1922. Serial No. 584,601.

To all whom it may concern:

Be it known that I, CILIRLES A. BUTCHER,

a citizen of the United States, and a resident of East Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Automatic Switching Systems, of which the following is a specification.

My invention relates to automatic systems and particularly to systems employed in controlling the operation of automatic substations.

One object of my invention is to provide an automatic system for controlling the starting of a synchronous converter and the development of a predetermined polarity at -the direct-current end.

Another object of my invention is to provide a system, of the above-indicated character, in which the development of the predetermined polarity is controlled by a polarity-responsive relay while starting voltage is applied to the converter whereupon the starting voltage is removed and normal operating voltage applied to the converter.

Another object of my invention is to provide a system, of the above-indicated character, in which a sufficient time element is introduced between the removal of the starting voltage from the converter and the application of the normal operating voltage thereto to permit the dissipation of hot gases from between the terminals of the switching means by which the starting voltage is applied to the converter.

A further object of my invention is to insert such time element between the operation of the starting and the running switches by means of definite steps introduced by consecutively operating relays that shall also be operative to control the disconnection of the polarity controlling means.

A further object of my invention is to provide a system, of the above-indicated character, employing a field-reversing switch to control the development of a pre determined polarity, in which resistance means'is rendered effective or'inefiective in the circuit of the shunt field winding to control the degree of excitation of the field- "magnet pole members in accordance with the polarity during starting conditions and rendered ineffective after the correct polarity is developed to permit the full excita- 55. tion of the field winding.

Patent No. 1,435,229, issued Nov. 14, 1922 to F. C. I-Ianker and C. McL. Moss, and assigned to the WVestinghouse Electric Manufacturing Company, describes an automatic substation in which alternating-cur rent energy is translated into direct-current energy by a synchronous converter. In order to permit the connection of the converter to the direct-current circuit always in the same manner, a predetermined polarity is developed in the converter. The development of such polarity is .controlled by energizing the field winding in a predeter mined direction from the commutator of the converter. Should the polarity be developed in the wrong direction, it is reversed and developed in the right direction by reversing the field winding and slipping a pole. A polarized relay that is responsive to the polarity that is developed at the direct-current end of the converter is employed to control the operation of the fieldwinding switch.

In a copending application, Serial No. 592,749, automatic station switching, filed Oct. 6, 1922, by S. G. Leonard and assigned to the assignee of the present. application, means are disclosed and described for locking a rotating electrical device out of service if its running switch is not closed within a predetermined interval of time after the closing of its starting switch. In practicing my invention, I utilize the general scheme of connections that is disclosed in the above-mentioned application. In order to limit the excitation of the field-magnet pole members if the polarity should be developed in the wrong direction, I provide a resistor in-the circuit of the shunt field winding thatv efi'ectively limits the excitation of the field winding while starting voltage is applied to the converter.

If the wrong polarity is developed, the resistor is eliminated from-the circuit of the field winding when thewinding is connected to the converter in a reversed sense, to permit a quick 2nd increased degree-of reversing eXcit-ati If the polarity is developed in the right direction, the starting voltage will be removed and the full oper ating voltage will be immediately applied to the converter and the resistor short circuited to permit the field excitation to'be quickly increased.

It has been observed that, in various applications where the transfer from starting to running conditions is too quickly made, as by means of a single transfer relay, the hot gases present between the contact members of the starting switch, immediately after the opening thereof, serve as a highresistance short circuit when the running switch is closed. In order to permit the dissipation of such gases as may be developed at the contact members of the starting switch, I provide a definite sequence of relay operatlons between the opening of the starting switch, and the closing of the running switch to provide a sufficient interval of time to permit the dissipation of such gases.

Since the polarized relay need be connected to the converter only during the starting operation and in order to render it as sensitively responsive as possible, the relay windings are constructed to operate in response to the direct-current electromotivev force that is generated during the starting operation.

In order to preclude the application of increased direct-current electromotive force, as would be the case when the running switch is closed, I employ the relay operations that control the transfer from starting to running conditions to also disconnect the polar- .ized relay. 7

Figure 1 of the accompanying drawings is a diagrammatic view of an electrical system embodying my invention.

Fig. 2 is a schematic diagram showing, in simplified manner, the individual circuits that control the energization of the respective operating coils associated with, and controlled by, such circuits.

In referring to the accompanying drawings, the main and interlock switches of all of the apparatus are shown in the individual circuits of the schematic diagram of Fig. 2 in the de-energized position of the control device or apparatus with which the respective switches are associated.

In the system that is illustrated, energy is received from an alternating-current circuit 1 through a circuit interrupter, or other switching means 2, and a plurality of power transformers 3 by a rotary transformer or synchronous converter 4 which translates such energy into direct-current energy which is thereupon supplied to a direct-current circuit, such as a trolley circuit 5, through a switching device 6.

When the voltage of the direct-current circuit 5 decreases to a predetermined value indicating a demand for energy,- a voltage relay 8 becomes sufiiciently de-energized to close its switch The coil of relay 8 is connected between the trolley circuit 5 and ground, as shown in individual circuit A of the schematic diagram.

When the demand upon the circuit 5 is manifested by the decrease of :voltage and the consequent closing of the relay switch 8, various control devices,to be described later, are operated to close the main switch 2 and energize the transformers 3. All but two brushes of opposite polarity are then raised from the commutator cylinder by a brushraising mechanism 9, and a starting switch 10 is then closed to impress a starting voltage of relatively small value upon the converter windings to start the converter and accelerate it to synchronous speed. At synchronous speed, the converter develops its polarity at random. If such polarity is a predetermined polarity corresponding to the polarity of the trolley circuit, the starting switch 10 will be opened and a running switch 11 closed to remove the starting voltage and to supply normal operating voltage to the converter. The brush-controlling mechanism 9 is thereupon operated to lower the brushes to the commutator cylinder, after which the converter is connected to the trolley circuit through the switch 6. I

If, while the starting voltage is applied to the converter, the converter should evelop a polarity reverse. to that of the direct-current circuit, a (polarity-responsive relay 12, that is energize through the two unraised brushes, will control the reversing of the field winding 13 of the converter b means of a field reversing switch 14. A ter the converter polarity is reversed and then built up in the right direction, the field winding is connected in the proper manner to permit its energization always in the same direction, after which, the transfer is made from starting to running condition.

In order that the degree of excitation of the field winding and of the field-magnet ole members may be limited when the polar- 1ty is developed in the reverse direction, a resistor 15 is disposed in circuit w1th the field winding, that is effective while the winding is connected to the converter brushes m the proper manner but which 1s el m nated from the circuit when the field winding 18 reversed by the polarized relay to reverse the excitation of the field-magnet pole members.

If the polarity is developed in the wrong direction, the resistor 15 is, of course, effective in limiting the excitation only while the polarity is being developed in such wrong direction. If the polarity is developed in the right direction, the resistor 15 is immediately short-circuited during the transfer from starting to running con ition.

A relay 16 is disposed in the circuit of the field winding and is effective to preclude the connection of the converter to the directcurrent circuit if the circuit of the field winding should be open and is similarly effective to disconnect the station if the circuit paratus is derived from the alternating-current circuit 1 through an auxiliary transformer 17 and a switch 18 which is provided to manually disconnect the station equipment from the source of control energy when it is desired to inspect the apparatus.

Upon referring to individual circuit B of the schematic diagram, it will be seen that, when the relay switch 8 closes, by reason of the decreased voltage on the direct-current circuit 5, a circuit will be completed between a control bus W and a control bus Y which controls the energization of a relay 19. This circuit may be traced from the bus conductor Y through the switch 8 in its deenergized position, the operating coil of the relay switch 19 and an interlock 20 that is closed when the main interrupter 2 is open, to the control bus conductor W.

A single-pole, double-throw, manually-operable switch 21 is associatedwith the relay switch 8 and is adapted,when closed in the upper position, to short-circuit the switch 8. The switch 21 is closed in its upper position when it is desiredto start the station manually and in its lower position when the station is to be automatically started in response to a predetermined voltage condition in the direct-current circuit 5.

Upon referring to circuit D, it Will be ob .ing coil of a master relay from control bus conductor Y through the operating coil of relay switch 30 to control bus conductor Z. The relay 30, when energized, closes three switches 31, 32 and 33, respectively.

Switch 31, when closed, connects the main control bus conductor Z to an auxiliary con trol bus conductor X from which the control 1 devices operating subsequently thereto are energized. Thus, upon the opening of the switch 31, the control devices may be s1multaneously and quickly yle-energized to dis -onneet the converter from the system.

Switch 33, of relay 30, when closed, shortcircuits relay switch, 19 and the neutrallypositioned switch 24 of the polarized relay, thereby maintaining a holding circuit for the relay 22. These circuit relations are more clearly apparent from the circuits D and E in the schematic diagram. Relay 22 energizes relay 30, which, in turn, maintains the energizing circuit for relay 22.

switch 11 is open, the raising coil 34 of the,

brush-operating mechanism, a limit switch 3'? and the conductor 27 to the control bus conductor Y. The brush mechanism is thereupon operated to raise all but two of the brushes from the commutator cylinder.

The brush raising operation is maintained until the circuit of the raising coil 34 is opened by the limit switch 37. In this position, an interlock switch 38 is closed which energizes the operating coil of a relay 39, as is shown in circuit F. Relay 39 is the control relay for the starting switch 10. The circuit may be traced from the bus conductor Y through the conductor 27, the interlock switch 38 of the brush-operating mechanism, the operating coil of the relay 39, an interlock switch 40 that is closed when the running switch 11 is open, and an interlock switch 41 that is controlled by 'a transfer relay 42 to th auxiliary bus conductor X. The relay 39 i, thereupon energized to close three switches 43, 44 and 45, respectively.

Switch 43, of relay 39, when closed, co1npletes the circuit, G, of the operating coil of a relay 46 from the auxiliary control conductor X, through the switch 43, a resistor 47 and the operating coil of the relay 46 to control bus conductor Y. Relay 46 and a relay 48 control the closing of the interrupter 2.

The relay 46 closes its switch to energize the operating coil of relay 48, which circuit may be traced, as seen in the right-hand portion of circuit G, from bus conductor X through switch 43, relay switch 46 and operating coil of relay 48 to control bus conductor Y. The relay switch 48, when closed, connects the closing coil 49 of the main switch 2 between the main control conductors Y and Z, as shown in circuit H, whereupon the interrupter 2 is closed. Since the interrupter 2 is provided with a low-voltage trip coil 51 for holding the interrupter closed when the voltage of the circuit 1 is normal, the closing coil 49 may be dc-energized after the interrupter is closed,

An interlock switch 50, that closes with the main contact members of the-interrupter 2, energizes circuit I including the low-voltage coil 51 of the interrupter 2 and an auxiliary time-element relay 52 which closes its. contact members a few seconds after be ng energized to short-circuit the coil-of the relay 46, as shown in the left portion of circuit G. The relay 461s thereupon de-energized to open its switch, and the relay switch 48 is thereupon permitted to open, thereby de-energizing the closing coil of the interrupter 2.

Simultaneously with the operation of the respective relays 46 and 48 that eliect the closing of the main interrupter 2, the interlock switch 45 of the relay 3S) completes the circuit including the operating coil of the starting switch 10 to effect the closing of that switch to apply starting voltage to the converter. This circuit may be traced, as shown in circuit J, from control bus conductor Y through conductor 27, the interlock switch 38 of the brush-controlling mechanism, the switch 45 of relay 39 and the operating coil of the starting switch 10 to the control bus conductor X. Starting voltage is applied to the converter which is then ac-. celerated to synchronous speed.

Let it be assumed that the converter at: tains synchronous speed with the reverse polarity. The starting switch 10, when closing, closes an interlock switch which connects the windings of the polarized-relay device 12 across the two unraised brushes of the commutator cylinder of the converter. This circuit may be traced, as shown in the circuit K of the schematic diagram, from the desired positive brush of the converter through conductor 56, a normally closed interlock switch 57 that is closed by the fieldreversing switch 14, the interlock switch 55 of the starting switch 10, an armature winding 58 and a clutch winding 59 of the polar-- ized relay 12, and a conductor 60 to the desired negative brush of the converter.

The polarized relay 12, immediately upon being energized, secures the rotating member of the motor to the movable arm 24 by means of the magnetic clutch coil 59. It" the polarity is in the reverse direction, as has been assumed, the movable contact member 24 will gradually be actuated to bridge the contact members 61, whereupon a relay 62,

to control the field switch 14, will be energized, as shown in circuit L, by being connected directly across the brushes of the converter between the conductors 56 and 60.

The relay 62, when energized, closes two switches 63 and 64, respectively. Switch 64 completes a holding circuit to maintain the relay winding connected between the converter brushes so long as the potential difference across the brushes is sufiicient to maintain the relay energized to hold the same closed.

The switch 63, when closed, completes the energizing circuit for the operating coil of the reversing switch 114, as shown in circuit M. This circuit may be traced from control busconductor Y through conductor 27, the interlock switch 38 of the brush-control mechanism, the switch 45 of the relay 39, the

switch 63 of the relay 62 and the operating coil of the field switch 14 to the control bus conductor X. The field winding is thereupon connected to the brushes of the converter commutator in a reverse manner, thereby reversing the excitation of the fieldmagnet pole members.

As the electromotive force developed by the converter gradually decreases to zero, the voltage available to maintain the relay 62 energized decreases until it is insufficient to maintain that relay in its energized position. The switches 63 and 64 are thereupon opened. Switch 63, when open, de-energizes the circuit of the-operating coil of the field switch 14 which is thereupon actuated to its normal postion by operating springs 64a. The converter will then slip a pole and develop the polarity in the right direction.

If, for any reason, the polarity should again come up in the wrong direction, the same reversing operation will be effected until the correct polarity is developed in the converter. Normally, however, little ditficulty is encountered in such reversing operations and, ordinarily, one reversal is sufficient to reverse the polarity to cause it to be developed in the right direction.

When the polarity is developed in the right direction, the polarized relay 12 actuates the bridging member 24 to engage the contact members 65 which completes the energizing circuit of the operating coil of the transfer relay 42, as illustrated in circuit N, from control bus conductor Y through switch contact member 65 of the polarized relay and the operating coil of the relay 42 to control bus conductor X. A switch 66 is closed when the operating coil of the relay 42 is energized and is connected in parallel with the contact members 65 of the polarized relay 12 to maintain a holding circuit for the operating coil of relay 42 after it is once energized.

The transfer relay 42, when energized, opens its switch 41 and closes, in addition to the switch 66, another auxiliary switch 67. The switch 41, when opening, opens the circuit of the operating coil of the control relay 39 for the starting switch 16, as shown in circuit F.

The starting switch 10 thereupon opens, and, when in full-open position, closes an auxiliary interlock switch 68 and opens a switch 69. As is shown in the schematic circuit P, the interlock switch 68, of the starting switch 10, when closed, co-operates with the interlock switch 67 of the transfer relay 42 to energize the circuit of a control relay 70 for the running switch ll by connecting the operating coil between the control bus conductors X and Y.

The relay 70, when actuated to its ene7rgized position, closes two switches 71 and 2. operating coil of the running switch 11 directly to the control bus conductors X and Switch 71, when closed, connects the 76 of the brush-control Y, as shown in circuit Q, whereupon the running switch 11 is closed to apply normal operating voltage to the converter windings. The converter is now in proper condition to be connected to the direct-current circuit.

In order to permit the converter to build up or develop its voltage quickly, the switch 72 of the relay 7 0 short-circuits the resistor 15 that is connected in series with the field winding. The limiting effect of the resistor being thus eliminated, the excitation of the field winding is permitted to increase rapidly.

The brushes of the commutator may now be lowered. The control circuit for effecting the lowering of the brushes may be traced, as will be seen by referring to schematic circuit E, from control bus conductor Y through conductor 27, limit switch 75, operating coil 76 of the brush-control mechanism 9, an interlock switch 77 that is closed when the main switch 11 is closed, and the switch of the relay 22 to the control bus conductor Z. The lowering coil mechanism will therefore be energized to lower the brushes to the commutator cylinder, after which the limit switch 7 5 will be opened.

While the brushes are being lowered. the field excitation is being increased until finally such excitation attains a value suflicient to energize and operate thefield relay 16 which thereupon closes its two switches 78 and 79. The switch 78, when closed, cooperates, as shown in circuit R, with an interlock switch 80 that is closed when the brushes are lowered to the commutator cylinder, and the interlock switch 32 of the master relay 30 to complete an energizing circuit for the operating coil of a relay 81 to control the closing of the directcurrent switch 6. The circuit be traced from bus conductor Y through conductor 27, the interlock switch 80 of the-brush mechanism, the interlock switch 78 ot the field relay 16, the operating coil of relay 81. a conductor 82 and the interlock switch 32 of the master relay 30 to control bus conductor X. The relay 81 is thereupon energized to close its switch 83. After the brushes are lowered and the field winding is sufiiciently energized, the converter is connected to the direct-current circuit.

Switch 83, of the relay 81, when closed, completesthe circuit of the operating coil of the direct-current switch 6, as shown in schematic circuitR. This circuit may be traced from control bus conductor Y through the operating coil ofi switch 6, the switch 83 of relay 81, the conductor 82 and\ the switch 32 of the master relay 30 to the control bus conductor X. The switch 6 is thereupon closed toconnect the converter 4 to the direct-current circuit 5.

Switch 6, when closed, closes an auxiliary interlock switch 85. Switch 85, when closed, connects main control bus conductor Z to the auxiliary control bus conductor X and is connected in parallel relation to switch 31 of master relay 30. The switch 85 is larger than the switch 31 and serves to conduct current to the auxiliary control bus conductor X during the continued operation of the converter.

If the demand should decrease to, or below, a predetermined value for a predetermined interval of time. it is desired to shut down the station to obviate the expense of running the machine idly. A timing relay 100 is therefore employed which may be adjusted to operate at difierent time intervals from the range of approximately three minutes to one-half hour which serves to disconnect the converter from the system when the demand on the station decreases to a predetermined value for a predetermined interval of time corresponding to the setting of the relay. The operation of this relay may be more readily understood by reference to schematic circuit C.

The circuit of the operating coil of the timing relay may be traced from the auxiliary control bus conductor W through a conductor 101, the operating coil of timing relay 100, the switch 120 of underload relay 90, a conductor 102, an interlock switch 103 that is closed when the normal voltage running switch 11 is closed, a conductor 104 and the switch 21 in its lower position to the control bus conductor Y. Y

The switch 120 of the underload relay will be closed only when the current taken from the converter is less than a prede termined value. Vi hen timing relay 100 is energized for a predetermined interval of time, it will close a switch 105 that may be adjusted for any time interval within the operating range of three to thirty minutes. When the switch 105 of the timing relay 100, operating in response to the time and the demand, closes. it effects the disconnection 'of the converter from the system by short-circuiting the operating coil of the relay 22, whereupon the operating switches and the control devices for the converter are de-energized and actuated to their respective open positions. The switch 105 short-circuits the operating coil of the control relay 22, as will be seen by referring to the schematic circuit D. Such connection is made through two conductors 106 and 107. I

The operating coil of the relay 22-is then ole-energized, permitting the switch to open and de-energize the operating coil of the master relay 30, whereupon the auxiliary control bus conductor X is disconnected from the bus conductor Z by the switch 31.

- The same conductors are then disconnected by the switch 85 of the main direct-current switch 6, since the operating coil of the switch 6 is de-energized by the opening of switch 32 of the master relay 30. This operation is more readily apparent by reference to'schematic circuit R.

The timing relay 100 is also provided with an additional timing element 110 which is employed as a protective feature during the starting operation of the converter to disconnect the converter from the alternating-current circuit and to lock out the control apparatus to preclude the automatic rcconnection of the converter until the station is visited by an inspector and the trouble cleared.

The timing element switch 110 is normally adjusted to be closed after an interval of approximately one minute to one and onehalf minutes, which interval of time is deemed sufficient to permit the development of a predetermined polarity and the transfer from starting conditions to running conditions by transferring from starting switch 10 to running switch 11. If such transfer is not made within the interval for which the time-element switch 110 is adjusted, the switch 110'closes to energize the circuit of a lock-out relay 111 which maintains a short-circuit across the operating coil of the relay 22 until the relay 111 is reset by hand.

The lock-out relay 111, when operated, short-circuits the operating coil of the re lay 22 by connecting the conductors 106 and 107, which may be more readily understood by referring to schematic circuit D.

When the transfer from starting to running conditions is not made within a predeterminedinterval. such condition is normally indicative of frozen hearings or other a trouble that will preclude normal operation of the converter. It is desirable, therefore, to prevent entirely any automatic operation of the converter until the station is visited and the trouble eliminated.

Under certain conditions, it is desirable and essential that the apparatus should not function to effect the immediate connection of the converter to the system. For example, if there has been no demand on the station for a predetermined interval. of time and the time-delay relay operates to disconnect the station, it is possible that the voltage of the direct-current circuit may decrease to effect the initiation of the starting apparatus immediately after the disconnection of the converter.

Inasmuch as the converter is yet rotating. at synchronous speed, if the converter were connected to the starting taps of the transformer, a false indication of correct polarity would immediately effect the. connection of the converter to the normal operating connections of the transformer. Since the indication of correct polarity was due to the.

plication of full operating voltage to the converter, the operation of the initiating and controlling relays 22 and 80 is precluded until the field excitation decreases to or below a predetermined value. That operation is controlled by means of the switch 79 of the field relay 16 and an interlock switch 112 of the main circuit interrupter 2 that is closed when the interrupter is opened. Thus, if the interrupter is openedwhile the field relay 16 is energized and its switch 79 is maintained closed, the operating coil of the relay 22 will be short--circuited to preclude its enegization until the switch 79 of the field relay 16 is opened. This operation may be more readily visualized upon reference to the left-hand portion of schematic circuit D.

When the field winding is reversed to reverse the excitation andthe polarity of the converter, it is desired to render the polarized relay absolutely non-operative. An interlock switch 113 is therefore closed, when the field switchd l is operated to its reversing position, that cooperates with the conductor and the interlock switch 55 of the starting switch 10 to short-circuit the polarized relay windings. The polarized relay is consequently actuated to its initial neutral position to be available for immediate operation when the wrong polaritv is reversed to the correct direction.

Overload relays 11 1 are provided that serve also to energize the loclcout relay 111 when an excessive overload occurs on the.a-lternating-current end of the converter which is sufficiently excessive to indicate abnormal conditions within the station.

In order to preclude operation of the converter, under low-voltage, single-phase or reverse-phase conditions, a relay 115 is provided that is responsive to such conditions to permit the closure of its switch if any one of such conditions occurs. The re lay 115, also, short-circuits the operating coil of the relay 22 to effect immediate disconnection of the converter from the system. After the disconnection of the converter, however, the switch opens to permit the reenergization of the relay 22.

By arranging the protective devices to control the energization'of the relay 22 according to the faulty conditions that occur, the protective devices may be arranged to distinguish between temporary abnormal conditions and for resisting faulty condi tions. In the former case, the machine is merely disconnected temporarily, whereas, in the latter case, the apparatus is arranged to maintain such disconnection and preclude the automatic reconnection until the faulty conditions are eliminated.

By providing several distinct steps in the transfer from starting to running conditions, I disconnect the polarized relay from the terminals of the converter that serve thereby to preclude an application of the increased voltage to the windings of the polarized relay when normal operating voltage is impressed upon the converter.

By means of the limiting resistor which I place in the circuit of the field winding, I preclude excessive excitation of the fieldmagnet pole members when polarity is cleveloped in the wrong direction, and permit normal excitation, when polarity is in the correct direction, by short-circuiting such resistor.

I have illustrated merely schematically the operation of the various control devices and it will, therefore, be understood that changes may be made in the structure and in the arrangement of the devices without departing from the spirit and scope of my, invention, as set forth in the appended claims.

I claim as my invention:

1. The combination with an alternatingcurrent circuit and a synchronous dynamoelectric machine to be energized therefrom, of means for applying a reduced electromotive force to the windings of the machine to start and to accelerate the machine to synchronous speed, meansfor subsequently applying the normal operating electromotive force to the windings, and controlling -means for rendering the former means ineffective and the latter means ettective and for introducing a time interval between such operations to permit said controlling means to be rendered non-effective before the norelement suflicient to permit the dissipation of conducting gases that may be formed by said means and then rendering the secondmentioned means effective. i

3. In an electric system, the combination with an alternating-current circuit, a transformer and a synchronous converter, of switching means for applying a reduced starting voltage to the converter from the transformer, means for applying the normal running voltage to the converter, and means responsive to the development of a predeter mined polarity in the converter for rendering the tirst-n'ientioned means ineffective and the. second-mentioned means effective and .for introducing a time interval between said operations to permit the dissipation of gases developed at the contact members of the first-mentioned switching means.

4. In an electric system, the combination with an alternating-current circuit, a transformer and a synchronous converter, of switching means for applying a reduced starting voltage to the converter from the t ansformer. means for applying the normal running voltage to the converter, and polarity-responsive means for controlling the operation of the said voltage-applying means and for introducing a predetermined time interval between the opening of the tirst-n'ientioned means and the actuation of the second-mentioned means to permit the disconnection of the polarity-responsive means before the actuation of the second means.

In an electric system, the combination with an alternating-current circuit, a transiormer and asynchronous converter, of

switching means for applying a. reduced starting voltage to the converter from the transformer, means for applying the normal running voltage to the converter, operating coils for said means, a relay for controlling the circuit of the coil of the second-mentioned means, means responsive to a synchronous condition of the converter for rendering the operating coil of the firstmentioned means inoperative to permit said means to open and then co-operating with the first-mentioned means to energize the control relay associated with the secondmentioned means. and means tor rendering the synchronous condition means non-responsive before the actuation of the second mentioned voltageapplying means.

6. In an electric system, the combination with an alternatingcurrent circuit, a trans former and a synchronous, converter, of switching means for applying a reduced starting voltage to the converter from the transformer, means for applying the nor mal running voltage to the converter, and means for precluding the operation of the running means until suflicient time has elapsed for the. hot conducting gases formed upon the opening of the starting means to be dissipated, comprising a relayfor the starting means, a relay for the running means and a transfer relay for controlling said relays.

7. In an electric system, the combination with an alternating-current circuit, a transformer and a synchronous converter, of

switching meansfor applying a reduced starting voltage to the converter from the transformer, means for applying the normal running voltage to the converter, and

means for precluding the operation of the running means until sufficient time has elapsed for the hot conducting gases formed uponthe opening of the starting means to be dissipated, comprising a relay for the starting means. a relay for the running means, a transfer relay for controlling said relays, and means responsive to a synchronous condition of the converter for controlling the transfer relay.

8. In an electric system, the combination with an alternating-current circuit, a transformer and a synchronous converter, of switching means for applying a reduced starting voltage to the converter from the transformer, means for applying the normal running voltage to the converter, and means for precluding the operation of the running means until sufficient time has elapsed for the hot conducting gases formed upon the opening of the starting means to be dissipated, comprising a relay for the starting means, a relay for the running means and a transfer relay for controlling said relays, and means responsive to a predetermined polarity developed in the converter for controlling the transfer relay.

9. In an electric system, the combination with an alternating-current circuit, a trans former and a synchronous converter, of switching means for applying a reduced starting voltage to the converter from the transformer, means for applying the normal running voltage to the converter, and means for precluding the operation. of the running means until sufficient time has elapsed for the hot conducting gases formed upon the opening of the starting means to be dissipated, comprising a relay for the starting means, a relay for the running means, a transfer relay for controlling said relays,

means responsive to a synchronous condi-- tion of the ,converter for controlling the transfer relay, and means for disconnecting the synchronous condition means before the actuation of the running voltage applying means.

10. In an electric system, the combination with an alternating-current circuit, a transformer and a synchronous converter, of switching means for applying a reduced starting voltage to the converter from the transformer, means for applying the normal I running voltage to the converter, and means for precluding the operation of the running means until sufficient time has elapsed "for the hot conducting gases formed upon theopening of the starting means to be dissipated, comprising a relay for the starting meangga relay for the running means, a i ;transfer relay for controlling said relays,

running voltage to the converter, and means for precluding the operation of the running means until sufficient time has elapsed for the hot conducting gases formed upon the opening of the starting means to be dissipated, comprising a relay for the starting' means, a relay for the running means, a transfer relay for controlling said relays, means responsive to a predetermined polarity developed in the converter for controlling the transfer relay, and means for disconnecting the polarity-responsive means before the actuation of the running voltage applying means.

- 12. In an electrical system of distribution, the combination with an-alternating-current circuit, a direct-current circuit and a synchronous converter for translating energy therebetween, of means for applying a reduced starting: voltage to the converter,

means for applying the normal running voltage thereto,,individual relays for the re spective voltage-applying means, a transfer relay for rendering ineffective the relay associated with the starting means and rendering effective the relay associated with the running means, means dependenuupon the converter developing a predetermlnd polarity corresponding to the polarity of the direct-current circuit for controlling the operation of the transfer relay, and means for disconnecting the polarity means after the operation of the transfer relay and before the actuation of the running voltage applying means.

13. In an electrical system of distribution, the combination with an alternatingcurrent circuit, a direct-current circuit and a synchronous converter for translating energy therebetween, of means for applying a reduced starting voltage to the converter, means for applying the normal running voltage thereto, individ'ua relays for the respective voltage-applying means, a transfer relay for rendering inefi'ective theirelay associated wit the starting means and rendering effective the relay associated with the running means, and means for raising certain of the main brushes from the commutator cylinder and for precluding the operation of the starting-means -relay until said brushes are raised a predetermined extent. a

. relatively 14. In an electrical system of distribution,

means for applying the normal running voltage thereto, individual relays for the respective voltage-applying means, a transfer relay for rendering ineffective the relay associated with the starting means and rendering effective the relay associated with the running means, and means for precluding the operation of the starting-means relay unless both the running means and the transfer relay are in non-operative position.

15. In an electrical system of distribution, the combination with an alternating-current circuit, a direct-current circuit and a synchronous conver er to be connected therebetween, of switching means .for applying starting and running voltages to the converter from the alternating-current circuit, a transfer relay for rendering the starting means non-operative and the running means operative, means responsive to a predetermined polarity in the converter for rendering the transfer relay operative, auxiliary means for maintaining the transfer relay in operativev condition after the starting means is rendered inoperative and means for rendering said polarity-responsive means inoperative after the transfer relay is actuated to said operative condition.

16. The combination with a synchronous converter provided with a shunt field winding and means for consecutively applying low starting and normal operating electromotive forces to the converter, of means for limiting the current that may traverse the field winding while the start ing voltage is applied thereto and means for rendering such limiting means ineffective 'when the'transfer from starting to operating condition is efl'ected.

17. The combination with a synchronous converter provided with a shunt field wind ing and means for consecutively applying relatively low starting and normal operating electromotive forces to the converter, of a resistor in circuit with the field Winding to limit the current that may traverse the same duringstarting operation and means for short-circuiting the resistor when transferring to the normal operating condition. 18. The combination with an alternatingcurrent circuit, a direct-current circuit and a converter provided with. a shunt field winding to be connected therebetween, of means for applying a reduced starting voltage to the converter to permit the development of chance polarity at the direct-current end of the converter, means associated with the field winding to limit the degree of excitation of the winding and means dependent upon the development of a predetermined polarity for rendering such limiting means ineffective and controlling the application of-normal operating voltage to the converter. 1

19'. The combination with an alternatingcurrent circuit, a direct-current circuit and a converter provided with a shunt field winding to be connected therebetween, of means for applying a reduced starting voltage to the converter to permit the development of chance polarity at the direct-cur-- rent end of the converter, means associated with the field Winding to limit the degree of excitation of the winding if the polarity should be other than in a predetermined direction, means responsive to the polarity for then controlling the development of a predetermined polarit in the converter and for then rendering t means ineffective.

20. The combination with an alternatin current circuit, a direct-current circuit and a converter provided with a shunt field winding to be connected therebetween, of means for applying a reduced startingvoltage to the converter to permit the development of chance polarity at the direct-current end of the converter, switching means for controlling-the direction of excitation of the field winding having a normal operating position, means operative during'the starting period to limit the excitation of the field winding while the switching means occupies the normal operating position and means for rendering the limiting means ineffective when a predetermined polarity is developed in the converter while the switeh mg means is disposed in normal operatmg position.

21. The combination with an alternatingcurrent circuit, a direct-current circuit and a converter provided with a shunt field Winding to be connected therebetween, of means for. applying a reduced starting voltage tothe converter to permit the development of chance polarity at the direct-current end of the converter, switching means operative in one position to control the excitation in a direction corresponding tonormal operation and operative in another position to control the field excitation in the opposite direction, means responsive to the polarity of the converter for controlling the development.

of a predetermined polarity by controlling the switching means, means for limiting the field excitation when chance polarity develops, said means being rendered inelfective by the switching means in reversing position if thechance polarity be other than a predetermined polarity, and means for rendering the limiting means ineffective when the predetermined polarity is developed.

: =In an electrical system, the combination with an alternating-current circuit, a direct-current circuit, a rotary transformer provided with a shunt field-magnet winding for translating energy therebetween, means for consecutively applying relatively lOW starting and normal operating voltages from the alternating-current circuit to the transformer, and means for connecting the transformer to the direct-current circuit, of means for rendering said direct-current circuit conpredetermined value.

I 23. In an electrical system, the combination with an alternating-current circuit, a direct-current circuit, a rotary transformer provided with a shunt field-magnet winding for translating energy therebetween, and means for consecutively applying relatively low starting and normal operating voltages from the alternating-current circuit to the transformer of a'resistor connected in circuit with the field-magnet winding and means responsive to the development of a predetermined polarity in the transformer for short-circuiting the resistor and for maintaining said short-circuit while the transformer is translating energy between the two circuits.

In testimony whereof, I have hereunto subscribed my name this 5th day of August 1922.

' CHARLES A. BUTCHER. 

